Shader-内轮廓自发光效果

需求

1 基于涅菲尔反射的变形

• 原理 (近处的反射少，远处反射多)
  
  1)公式(近似)：F = Fscale + (1-Fscale)(1-v·n)^5
• 利用fresnel做边缘发光，代码

fixed fresnel = _FresnelScale + (1 - _FresnelScale) * pow(1 - dot(viewDir, worldNormal), _PowVal);//涅菲尔公式：_PowVal =5
_ColorFresnel * saturate(fresnel)

2 基于表面着色器Unity2019

Shader "Unlit/FirstShader"
{
	Properties
	{
			_MainTex(" Diffuse (RGB)", 2D) = "white" {}
			_NormalMap("Normal Map", 2D) = "bump" {}
    _RimColor ("Rim Color", Color) = (1.0, 1.0, 1.0, 0.0)
    //_RimConcentration ("Rim Concentration", Range(0.5, 5.0)) = 0.9
    _RimStrength ("Rim Strength", Range(1.0, 4.0)) = 1.45
	}
		SubShader
	{
		Tags { "RenderType" = "Opaque" }

		CGPROGRAM
		#pragma surface surf Lambert

		sampler2D _MainTex;
		sampler2D _NormalMap;
		float4 _RimColor;
		float _RimConcentration;
		float _RimStrength;

		struct Input
		{
			float2 uv_MainTex;
			float2 uv_NormalMap;
			float3 viewDir;
		};

		void surf(Input In, inout SurfaceOutput o)
		{
				fixed4 c = tex2D(_MainTex, In.uv_MainTex);
				float Lc = saturate(dot(normalize(In.viewDir), o.Normal));
				half rim = 1.0 - Lc;
				o.Albedo = c.rgb;
				o.Normal = UnpackNormal(tex2D(_NormalMap, In.uv_NormalMap));
				o.Alpha = c.a;
				//o.Emission = _RimColor.rgb * pow(rim, _RimConcentration);
				o.Emission = _RimStrength * (_RimColor.rgb * smoothstep(0.2, 0.6, rim));
		}
		ENDCG
	}
		FallBack "Diffuse"
}